1. Field of the Invention
The present application relates to a flexible display device and method of manufacturing the same, and more particularly, to a manufacturing method of a flexible display device adapted to enhance reliability and reduce defects.
2. Discussion of the Related Art
Nowadays, the display field has seen rapid development for visually representing an electrical information signal due to the wide spread of information society. In accordance therewith, a variety of flat panel display devices have been developed with such features as slimness, lightweight and low power consumption. Also, flat panel display devices have been rapidly replacing the existing cathode ray tubes (CRTs).
Examples of flat panel display devices are liquid crystal display (LCD) devices, organic light emitting display (OLED) devices, electrophoretic display (electric paper display (EPD)) devices, plasma display panel (PDPs) devices, field emission display (FED) devices, electroluminescence display (ELD) devices, elector-wetting display (EWD) devices, and so on.
Such flat panel display devices commonly include a flat display panel to realize an image. A flat display panel is typically configured with a pair of substrates that are combined to face each other, with an inherent light emitting ability or a polarizing material layer therebetween.
Also, various display devices have been actively developed to distinguished them from the existing designs, such as to enhance esthetic values and provide useful multi-functions. In general, a display device according to the related art includes a flat panel that uses a glass substrate and so on. Due to this, it is difficult to secure diversity in design. Moreover, the flat panel has different viewing distances between the central portion designed for the main viewing area and the side portion. In other words, the rigid flat panel causes a distance deviation between its central portion and its side portion with respect to the main viewing area.
To address this matter, a flexible display device using a flexible substrate made of, for example, a plastic material and so on has been developed. Such a flexible display device can be designed in a variety of shapes, which is different from the flat panel display device of the related art. Such a flexible display device is attracting public attention as the next generation display device which can replace the monitors of portable computers, electronic newspapers, smart cards and printed media such as books, newspapers, magazines and so on.
Various materials have been researched to make flexible display devices enhance esthetics value and become thinner and lighter. As such, a variety of flexible substrates are being applied to flexible display devices. Examples are a thin film metal sheet, a plastic material and so on. Since such flexible substrates are designed to be bent, it may be difficult to apply flexible substrates to the equipment used for manufacturing existing display devices, which is mainly designed for glass and quartz substrates. For example, it may be difficult for such flexible substrates to be fed by track equipment or a robot and received into a cassette or tray.
As such, flexible substrates are typically attached on a support substrate before forming device elements on their surfaces. The support substrate is used to support the flexible substrate during the formation of device elements, and then, the flexible substrate is separated from the support substrate.
In detail, the flexible substrate and the support substrate are adhered to each other with a sacrificial layer therebetween. The flexible substrate is exfoliated (or separated) from the support substrate by irradiating a laser beam onto the rear surface of the support substrate to treat the sacrificial layer. However, the sacrificial layer may not be sufficiently treated by the laser beam, when, for example, foreign materials are attached to the rear surface of the support substrate.
As a result, the device elements, which are formed on the flexible substrate at the untreated portions of the sacrificial layer, may be damaged during the separation process of the flexible substrate from the support substrate. In other words, the untreated portions may be generated in the sacrificial layer due to the foreign materials. This may cause a bright and/or dark spot in the flexible display device according to the related art.